Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is none, oncePerWeek, severalPerWeek or daily.
Build a proper factor for the responses below and store it in a variable w.
Print the factor.
Write the code to count the numbers of occurrences of each level and print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek oncePerWeek <NA> none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 x 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the results.
Next, understand why an error is generated and use replace argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor w from it.
Finally, count the numbers of occurrences of each level in w.
Ensure, that levels are in order provided in the variable lvl.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "oncePerWeek" "none" "daily"
sample( lvs, 3 )
[1] "severalPerWeek" "none" "daily"
sample( lvs, 3 )
[1] "none" "severalPerWeek" "oncePerWeek"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] daily severalPerWeek oncePerWeek daily severalPerWeek daily oncePerWeek oncePerWeek none oncePerWeek oncePerWeek none
[13] none oncePerWeek daily none none daily oncePerWeek daily severalPerWeek none oncePerWeek oncePerWeek
[25] severalPerWeek daily daily severalPerWeek daily oncePerWeek oncePerWeek daily severalPerWeek oncePerWeek daily none
[37] none oncePerWeek severalPerWeek oncePerWeek severalPerWeek severalPerWeek oncePerWeek daily oncePerWeek daily none oncePerWeek
[49] daily daily oncePerWeek severalPerWeek oncePerWeek daily daily daily severalPerWeek daily oncePerWeek daily
[61] oncePerWeek oncePerWeek daily daily oncePerWeek none daily daily oncePerWeek none oncePerWeek severalPerWeek
[73] none daily none oncePerWeek daily none daily severalPerWeek oncePerWeek oncePerWeek oncePerWeek none
[85] oncePerWeek daily severalPerWeek daily none daily daily oncePerWeek none oncePerWeek daily daily
[97] none severalPerWeek none severalPerWeek
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 x 2
f n
<fct> <int>
1 none 19
2 oncePerWeek 32
3 severalPerWeek 16
4 daily 33
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its levels.
The factor w from the previous exercise will be then shown in this order: none, oncePerWeek, severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed: daily, severalPerWeek, oncePerWeek, none.
Apply to w one of the fct_ functions from the tidyverse library to produce a factor w2 with the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 x 2
f n
<fct> <int>
1 daily 33
2 severalPerWeek 16
3 oncePerWeek 32
4 none 19